CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
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User’s Manual U14359EJ4V0UM
6.6.2 Flyby transfer
Since data is transferred in 1 cycle during a flyby transfer, a memory address is always output irrespective whether
it is a source address or a destination address, and read/write signals of the memory and peripheral I/O become
active at the same time. Therefore, the external I/O is selected by the DMAAK0 to DMAAK3 signals.
To perform a normal access to the external I/O by means other than DMA transfer, externally AND the CSm and
DMAAKx signals (m = 0 to 7, x = 0 to 3), and connect the resultant signal to the chip select signal of the external I/O.
A circuit example of a normal access, other than DMA transfer, to external I/O is shown below.
Figure 6-15. Circuit Example When Flyby Transfer Is Performed Between External I/O and SRAM
Ax to Axx
D0 to D7
OE
WE
CSn
SRAM
Ax to Axx
D8 to D15
OE
WE
CSn
SRAM
External I/O
D0 to D15
RD
WR
CS
Ax to Axx
D0 to D15
RD
LWR
CSn
UWR
V850E/MA1
IORD
CSm
IOWR
DMAAKx
Remark
n = 0 to 7, m = 0 to 7 (n
≠
m)
x = 0 to 3